forbes<-function(x,y,corrected)	{
	if (missing(corrected))	{
		corrected <- T
	}
	if (is.numeric(x) && is.numeric(y) && min(x) == 0 && min(y) == 0 && length(x) == length(y))	{
		a <- length(which((x * y) > 0))
		b <- length(which(x > 0)) - a
		c <- length(which(y > 0)) - a
	} else	{
		a <- length(na.omit(match(x,y)))
		b <- length(x) - a
		c <- length(y) - a
	}
	n <- a + b + c
	if (corrected == T)	{
		return(a * (n + sqrt(n))/((a + b) * (a + c) + a * sqrt(n) + (b * c)/2))
	} else	{
		return(a * n/((a + b) * (a + c)))
	}
}

forbesMatrix<-function(x,corrected)	{
	x[is.na(x)] <- 0
	m = matrix(nrow=ncol(x),ncol=ncol(x))
	for (i in 1:ncol(x))	{
		for (j in 1:ncol(x))	{
			m[i,j] = forbes(x[,i],x[,j],corrected)
		}
	}
	return(m)
}